First add the songs on your limewire (that you want on your ipod) onto the MP3 playlist, (below the list of your songs) to add songs highlight the song than click enqueue.
Next when you have all the songs you want on your MP3 playlist, highlight all the songs and click Save As... and save it under a folder that you will rememember where you saved it.
Next open up iTunes go under file>add file to library, and go under the folder you saved the playlist and click open and your songs will appear under your library.